// ASM: a very small and fast Java bytecode manipulation framework
// Copyright (c) 2000-2011 INRIA, France Telecom
// All rights reserved.
//
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// modification, are permitted provided that the following conditions
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//    notice, this list of conditions and the following disclaimer.
// 2. Redistributions in binary form must reproduce the above copyright
//    notice, this list of conditions and the following disclaimer in the
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//    this software without specific prior written permission.
//
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package cn.taketoday.context.asm;

/**
 * An edge in the control flow graph of a method. Each node of this graph is a
 * basic block, represented with the Label corresponding to its first
 * instruction. Each edge goes from one node to another, i.e. from one basic
 * block to another (called the predecessor and successor blocks, respectively).
 * An edge corresponds either to a jump or ret instruction or to an exception
 * handler.
 *
 * @author Eric Bruneton
 * @see Label
 */
final class Edge {

  /**
   * A control flow graph edge corresponding to a jump or ret instruction. Only
   * used with {@link ClassWriter#COMPUTE_FRAMES}.
   */
  static final int JUMP = 0;

  /**
   * A control flow graph edge corresponding to an exception handler. Only used
   * with {@link ClassWriter#COMPUTE_MAXS}.
   */
  static final int EXCEPTION = 0x7FFFFFFF;

  /**
   * Information about this control flow graph edge.
   *
   * <ul>
   * <li>If {@link ClassWriter#COMPUTE_MAXS} is used, this field contains either a
   * stack size delta (for an edge corresponding to a jump instruction), or the
   * value EXCEPTION (for an edge corresponding to an exception handler). The
   * stack size delta is the stack size just after the jump instruction, minus the
   * stack size at the beginning of the predecessor basic block, i.e. the one
   * containing the jump instruction.
   * <li>If {@link ClassWriter#COMPUTE_FRAMES} is used, this field contains either
   * the value JUMP (for an edge corresponding to a jump instruction), or the
   * index, in the {@link ClassWriter} type table, of the exception type that is
   * handled (for an edge corresponding to an exception handler).
   * </ul>
   */
  final int info;

  /** The successor block of this control flow graph edge. */
  final Label successor;

  /**
   * The next edge in the list of outgoing edges of a basic block. See
   * {@link Label#outgoingEdges}.
   */
  Edge nextEdge;

  /**
   * Constructs a new Edge.
   *
   * @param info
   *         see {@link #info}.
   * @param successor
   *         see {@link #successor}.
   * @param nextEdge
   *         see {@link #nextEdge}.
   */
  Edge(final int info, final Label successor, final Edge nextEdge) {
    this.info = info;
    this.successor = successor;
    this.nextEdge = nextEdge;
  }
}
